The present disclosure relates to an anode active material containing tin, iron, cobalt, carbon, and titanium as an element, a secondary battery using the anode active material, an electric power tool using the secondary battery, an electrical vehicle using the secondary battery, and an electric power storage system using the secondary battery.
In recent years, small electronic devices represented by a portable terminal or the like have been widely used, and it is strongly demanded to reduce their size and weight and to achieve their long life. Accordingly, as a power source for the small electronic devices, a battery, in particular, a small and light-weight secondary battery capable of providing a high energy density has been developed. In recent years, it has been considered to apply such a secondary battery not only to the small electronic devices but also to a large electronic devices represented by a vehicle or the like.
It has been examined to use various elements as a carrier (electrode reactant) of the secondary battery. Specially, a lithium ion secondary battery using lithium (Li) as an electrode reactant and using insertion and extraction of lithium ions as charge and discharge reaction has been largely prospective, since such a lithium ion secondary battery is able to provide a higher energy density than a lead battery, a nickel cadmium battery and the like.
As an active material of the anode in the secondary battery, in addition to a carbon material such as graphite, a metal material such as silicon (Si) and tin (Sn) is used for attaining a high capacity. However, in recent years, a new material has been progressively developed for the purpose of achieving a higher capacity and improving cycle characteristics and the like. Specifically, a low crystalline material which contains tin, cobalt (Co), and carbon (C) as an element, and in which the half-width of the diffraction peak obtained by X-ray diffraction is 1 deg or more has been examined (for example, see Japanese Unexamined Patent Application Publication Nos. 2006-107792, 2006-128051, 2006-344403, and 2008-293955). In the low crystalline material, in some cases, iron (Fe) is used instead of cobalt, and cobalt and iron are used together.